A copper mine in the Democratic Republic of the Congo. Photograph: Katrina Manson/Reuters

The London-listed mining company Eurasian Natural Resources Company (ENRC) has spent $550m (£340m) buying itself out of a Congo copper-mining partnership with the controversial Israeli billionaire Dan Gertler.

It comes as Gertler, who has been accused of making most of his $2.5bn fortune from "looting Congo at the expense of its people", declared he should be awarded a Nobelprize for his work developing the Democratic Republic of the Congo, which remains rooted to the foot of the UN's development index.

ENRC ended its relationship with Gertler this weekend after mounting pressure from politicians, investors and campaign groups demanding that it clean up its reputation and be more transparent in demonstrating how local people benefit from its activities.

The partnership ended when Gertler, who is close friends with Congo's president, Joseph Kabila, agreed to sell his family's 49.5% stake in Camrose Resources' Congo copper-mining assets to ENRC, which already owned the rest of the company.

The Congo operation has been highly controversial, with some critics claiming Gertler used his close relationship with the government to secure preferential treatment, and the Serious Fraud Office has been called on to investigate. Eric Joyce, an independent Scottish MP, had accused ENRC of "wrecking its reputation and integrity by entering into ropy deals with, frankly, shady middlemen". Gertler and ENRC deny the claims.

It comes a week after the International Monetary Fund froze loans to Congo because the government refused to publish details of a deal between a state-owned mining firm and companies said to be linked to Gertler. "Given the significance of natural resources in this economy and the huge impact that natural resources can have, we think it's very important to help DRC improve in terms of governance," Antoinette Sayeh, director of the IMF's African department, said.

British MPs are also demanding that the UK slash aid spending to Congo because the country has failed to show that profits from its mines are benefiting local people.

Jean Pierre Muteba, head of a group of NGOs that monitor mining in Congo's copper belt, said: "Dan Gertler is essentially looting Congo at the expense of its people. He has political connections, so state companies sell him mines for low prices and he sells them on for huge profits. That's how he became a billionaire." Gertler denies the claims.

The transparency campaign group Global Witness, which has criticised ENRC for using Congo partners that work with offshore companies which they claim could be benefiting corrupt local politicians, said: "Instead of the Congolese state benefiting from the sales of the country's most valuable mines, the bulk of the money is going to secretive companies in offshore countries, mainly in the British Virgin Islands.

"Mr Gertler and the FTSE 100 companies partnering up with him should publish full details of their dealings in the Congo, including the names of the offshore companies' beneficiaries. The public should be assured that these beneficiaries do not include corrupt Congolese officials".

Gertler, who is the grandson of the co-founder of Israel's diamond exchange, said it was the Congolese government's role to disclose the deals, not his. "We're a private company. Why should we announce?"

Despite its vast mineral wealth, Congo remains rooted to the bottom of the UN Development Programme's ranking of countries' income, health and education standards. Most of Congo's 68m population do not have access to electricity or running water, and one in five children die before their fifth birthday.

The nation's per capita income is $280 – below the level it was at when the country, formerly known as Zaire, gained independence from Belgium in 1960.